National home prices are up 7.3% in the fourth quarter over the same time frame a year. / Elise Amendola AP

by Julie Schmit, USA TODAY

by Julie Schmit, USA TODAY

Don't count on home prices rising as much as they did last year - a 7%-plus jump from the housing bust's bottom - economists say.

The Standard & Poor's Case-Shiller housing index, released Tuesday, showed national home prices up 7.3% in the fourth quarter over the same time frame a year earlier - the strongest move since 2006.

In nine of 20 cities measured, prices were up more than 9% in December vs. a year earlier, S&P says.

Phoenix led the way, with a 23% rise, followed by San Francisco at 14.4%.

"We had a burst coming out of the gate," says David Blitzer, chairman of S&P's index committee. Going forward, the rates of appreciation "will not be as aggressively beautiful as they've been."

The housing market hit bottom in the first quarter of 2012. That will make big jumps in year-over-year gains harder to achieve going forward, he adds.

What's more, some cities with big price jumps driven by investor buyers may not see a repeat this year, says Paul Diggle, economist with Capital Economics.

In Phoenix, for instance, last year's 23% jump was heavily fueled by investors who are turning single-family homes into rentals. When prices jump that much, they reduce rental returns, which lessens investor demand.

Investor interest may cool in those markets, but other cities will see price gains driven by strong job growth, lower vacancy rates and small foreclosure backlogs, Kolko says.

For this year, Capital Economics forecasts a 5% rise in national home prices. Market watcher Zillow forecasts a 3.3% jump vs. the 5.9% rise its data showed for last year.

Rising prices will enable more homeowners to sell, which will also hold down price gains, says Zillow economist Stan Humphries.

In January, the supply of existing homes for sale hit an almost eight-year low, helping to fuel bidding wars, the National Association of Realtors says.

More buyers are already looking at new homes. New-home sales jumped almost 16% in January from December to a 437,000 annual rate, the Commerce Department said Tuesday.

As new-home sales pick up, so will construction. That, too, will work to moderate price gains, Humphries says.

Home prices may be in for a rockier year than many predict, says Mark Hanson, who advises professionals on real estate trends.

Low interest rates, fueled by the Federal Reserve, have goosed home buyer demand and enabled buyers to pay more for homes, he says.

But the average 30-year fixed rate mortgage has been below 4% for more than 15 months, Freddie Mac data show. Rates edged up slightly last week, to 3.56% for the average 30-year fixed rate, and they're expected to go higher if the economy improves.

Higher interest rates will lead to a "hangover" for home prices, Hanson says.